Method for adhering decorative part to a vehicle

Abstract

A pressure sensitive adhesive consisting of a polyurethane foam is used for adhering decorative parts to automobiles and other vehicles. The adhesive is characterized by high tensile strength and elongation, excellent peel strength and good thermal and mechanical stress tolerance.

We claim:  
     
       1. A method for adhering a decorative part to a vehicle, comprising the steps of: 
       (a) applying a pressure sensitive adhesive consisting of a polyurethane foam having a density of about 20 to 55 lbs/cu ft to an inner surface of the decorative part; and  
       (b) joining the decorative part to a painted exterior surface of the vehicle by means of a bond formed by the polyurethane foam,  
       wherein the bond between the decorative part and the vehicle is free of any adhesive other than the polyurethane foam and the bond has an ASTM D-1000-87 peel test strength of at least 2 lbs/inch. 
     
     
       2. The method of  claim 1 , wherein the polyurethane foam comprises effective amounts of: 
       (a) a substantially linear polyether polyol having a monol molecule content greater than about 3 weight %, a functionality less than 2, a molecular weight of about 3,000 to 5,000 and a viscosity of about 700 to 1,500 centipoise at 25° C.;  
       (b) a modified polyisocyanate, comprising about 40-50 weight % 4,4′-diphenylmethane diisocyanate, about 15-25 weight % 2,2- and 2,4-diphenylmethane diisocyanates, about 10-20 weight % oligomers of the diphenylmethane diisocyanates, and less than about 2 weight % phenyl isocyanate, and having an isocyanate molecule content of about 25-30 weight %, a viscosity at 25° C. of about 100-200 mPa, and an equivalent weight of about 140-170;  
       (c) a thermal urethane catalyst; and  
       (d) a silicone surfactant,  
       wherein a foam is created by frothing a mixture comprising (a), (b), (c) and (d) to incorporate sufficient gas to yield a cured polyurethane foam density of 20 to 55 lbs/cu ft.  
     
     
       3. The method of  claim 2 , wherein the polyurethane foam further comprises at least one component selected from the group consisting of chain extender, pigment, solvent and epoxy stabilizer. 
     
     
       4. The method of  claim 2 , wherein the urethane catalyst is selected from the group consisting of organo-tin compounds and organo-tin compounds dissolved in an organic solvent. 
     
     
       5. The method of  claim 4 , wherein the urethane catalyst is stannous dioctoate. 
     
     
       6. The method of  claim 3 , wherein the chain extender is a dialkylene-glycol. 
     
     
       7. The method of  claim 6 , wherein the chain extender is dipropylene glycol. 
     
     
       8. The method of  claim 2 , wherein the polyurethane foam further comprises glass microbubbles. 
     
     
       9. The method of  claim 3 , wherein the epoxy stabilizer is a Bisphenyl A/epichlorohydrin. 
     
     
       10. The method of  claim 1 , wherein the polyurethane foam comprises: 
       (a) a substantially linear polyether polyol having a monol molecule content greater than about 3 weight %, a functionality less than 2, a molecular weight of about 3,000 to 5,000 and a viscosity of about 700 to 1,500 centipoise at 25° C.;  
       (b) a modified polyisocyanate, comprising about 40-50 weight % 4,4′-diphenylmethane diisocyanate, about 15-25 weight % 2,2- and 2,4-diphenylmethane diisocyanates, about 10-20 weight % oligomers of the diphenylmethane diisocyanates, and less than about 2 weight % phenyl isocyanate, and having an isocyanate molecule content of about 25-30 weight %, a viscosity at 25° C. of about 100-200 mPa, and an equivalent weight of about 140-170;  
       (c) a thermal urethane catalyst;  
       (d) a silicone surfactant; and  
       (e) a foam generator,  
       wherein sufficient gas is introduced into a mixture comprising (a), (b), (c), (d) and (e) by the foam generator to yield a cured polyurethane foam density of 20 to 55 lbs/cu ft.  
     
     
       11. The method of  claim 10 , wherein the polyurethane foam further comprises at least one component selected from the group consisting of chain extender, pigment, solvent and epoxy stabilizer. 
     
     
       12. The method of  claim 10 , wherein the urethane catalyst is an organo-tin catalyst. 
     
     
       13. The method of  claim 12 , wherein the urethane catalyst is selected from the group consisting of stannous dioctoate, organo-tin compounds, stannous dioctoate dissolved in dioctyl phthalate solvent, and organo-tin compounds dissolved in polyglycol solvent. 
     
     
       14. The method of  claim 11 , wherein the chain extender is a dialkylene glycol. 
     
     
       15. The method of  claim 14 , wherein the chain extender is dipropylene glycol. 
     
     
       16. The method of  claim 11 , wherein the epoxy stabilizer is a Bisphenyl A/epichlorohydrin. 
     
     
       17. The method of  claim 10 , wherein the foam generator is selected from the group consisting of glass microbubbles, blowing agents and combinations thereof. 
     
     
       18. The method of  claim 1 , wherein the decorative part comprises an anodized aluminum surface, the polyurethane foam is adhered to the anodized aluminum surface and the bond between the vehicle and the decorative part has an ASTM D-1000-87 peel test strength of at least 6 lbs/inch. 
     
     
       19. The method of  claim 1  in which the decorative part is an emblem or a piece of molding. 
     
     
       20. A method of adhering a decorative part to a vehicle comprising the steps of, 
       (a) applying a pressure sensitive adhesive layer consisting of a polyurethane foam having a density of about 20 to 55 lbs/cu ft to an inner surface of the decorative part;  
       (b) adding onto the pressure sensitive adhesive layer an interlayer of composition selected from the group consisting of acrylic adhesive, acrylic polymer primer, and a primer blend of acrylic polymer/hydroxy terminated polyvinyl chloride, and silane coupling agents; and  
       (c) contacting the interlayer composition with the vehicle thereby joining the decorative part to a painted exterior surface of the vehicle by means of a bond formed by the polyurethane foam and the interlayer composition;  
       in which the bond between the vehicle and the decorative part has a peel test strength of at least 6 lbs/inch by ASTM D-1000-87. 
     
     
       21. The method of  claim 20 , wherein the decorative part is formed from thermoplastic polymers. 
     
     
       22. The method of  claim 20  in which the decorative part is an emblem or a piece of molding.